Related Articles

Writing this week in the British journal Nature, scientists from the University of Wisconsin-Madison, the University of Paris, Cambridge University and St. Petersburg University in Russia report the discovery of a common genetic theme that provides powerful new evidence to firmly place nearly all animals -- from mollusks to humans -- on a simplified, three-limbed tree of life.

For more than a hundred years, scientist have depended on morphology, the form and structure of animals, to determine their place on the family tree. But over the past few years, a new tree has been proposed based on comparisons of themes found in animal genes.

"In the last four or five years, this tree has been totally reorganized and if you're interested in evolutionary relationships, that's really important," said Sean B. Carroll, a professor of molecular biology at the Howard Hughes Medical Institute at the UW-Madison and a co-author of the report in Nature.

The new genetic evidence suggests that in the animal kingdom there are three primary lines of descent that first diverged from a common ancestor at least 540 million years ago, and that gave rise to most animals (with the exception of jellyfish and sponges) living today, said Jennifer K. Grenier, a Howard Hughes Medical Institute Fellow, UW-Madison graduate student and a lead author of the report.

The new study was based on exploration of so-called Hox genes in three distinct kinds of animals: an unsegmented marine worm related to insects, an unusual marine animal called a lamp shell, and a segmented worm related to earthworms and leeches. Hox genes comprise part of a toolbox that is central to animal development. They help organize cells into the different body parts and determine such things as number and placement of legs, wings and other appendages.

By looking for, and finding, essentially the same critical organizing genes in seemingly unrelated animals, the groups from Wisconsin, Paris and Cambridge could, in essence, look far back in time and infer what critical body-organizing genes were present in a common ancestor.

"The point is we're trying to find out the early history of animal evolution," said Carroll, and what we've found is that "the genetic toolbox was pretty sophisticated in the earliest animals. That toolbox has been called on and expressed in many different ways."

It's possible, Carroll explained, to infer the past existence of some genes by looking at fossils, which may reflect those genes in the anatomy of the fossil animal. It is also possible to determine what critical genes were at work hundreds of millions of years ago by analyzing the genes of the living descendants of animals found in the fossil record.

"When you actually look at the genes, the three-branched tree is supported," Carroll said.

All of the animals involved in the new study, although from widely divergent parts of the animal kingdom, have similar Hox genes, although with slight but significant variations, said Grenier. The upshot, she said, is that an ancient common ancestor conferred these genes on animals that subsequently evolved in dramatically different directions.

"Before these (modern) animals existed, these genes were around. There was a common ancestor 600 million years ago that had all these genes," Grenier said.

The new, three-limbed tree simplifies the previous animal kingdom family tree by substituting one branch in place of many offshoots first suggested through anatomical comparison.

One intriguing upshot of the new study and others is that scientists, through genetic analysis, may learn something about the genes of an animal for which no fossil exists. Beyond 600 million years ago, the fossil record is skimpy at best, and scientists have no clue as to what the common ancestor of all animals actually looked like.

"There's no fossil. Five-hundred and forty million years ago is just about the end of the animal fossil record," said Grenier. "We don't know what (the common ancestor) looked like, but we think we know what its genes were."

More From ScienceDaily

More Plants & Animals News

Featured Research

Mar. 3, 2015 — While studying a ground-nesting bird population near El Reno, Okla., a research team found that stress during a severe weather outbreak of May 31, 2013, had manifested itself into malformations in ... full story

Mar. 3, 2015 — The 3-D printing scene, a growing favorite of do-it-yourselfers, has spread to the study of plasma physics. With a series of experiments, researchers have found that 3-D printers can be an important ... full story

Mar. 3, 2015 — Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Mar. 3, 2015 — By examining the forces that the segments of mosquito legs generate against a water surface, researchers have unraveled the mechanical logic that allows the mosquitoes to walk on water, which may ... full story

Mar. 3, 2015 — Pediatric otolaryngologists and surgeons are concerned with parents getting the wrong message regarding the safety/desirability of letting babies and young children eat peanuts to prevent them from ... full story

Mar. 3, 2015 — Researchers have developed a new way of rapidly screening yeasts that could help produce more sustainable biofuels. The new technique could also be a boon in the search for new ways of deriving ... full story

Mar. 3, 2015 — Similar to humans and animals, plants possess an innate immune system that protects them from invading pathogens. Molecular structures that only occur in pathogens enable their recognition and ... full story

Mar. 3, 2015 — For almost a century, scientists have been puzzled by a process that is crucial to much of the life in Earth's oceans: Why does calcium carbonate, the tough material of seashells and corals, ... full story

Mar. 3, 2015 — To simulate chimp behavior, scientists created a computer model based on equations normally used to describe the movement of atoms and molecules in a confined space. An interdisciplinary research ... full story

Featured Videos

Rare Goblin Shark Found in Australia

AFP (Mar. 3, 2015) — A goblin shark, a rare sea creature described as an &apos;alien of the deep&apos; is found off Australia and delivered to the Australian Museum in Sydney. Duration: 01:25
Video provided by AFP

Zookeepers Copy Animal Poses In Hilarious Viral Photos

Buzz60 (Mar. 2, 2015) — Zookeepers at the Symbio Wildlife Park in Helensburgh, Australia decided to take some of their favorite animal photos and recreate them by posing just like the animals. Jen Markham (@jenmarkham) has the story.
Video provided by Buzz60

Related Stories

Sep. 12, 2014 — Thoughts of the family tree may not be uppermost in the mind of a person suffering from a slipped disc, but those spinal discs provide a window into our evolutionary past. They are remnants of the ... full story

Sep. 3, 2014 — Scientists have discovered two new species of sea-dwelling, mushroom-shaped organisms. The new organisms are multicellular and mostly non-symmetrical, with a dense layer of gelatinous material ... full story

May 13, 2014 — A shared population of methicillin-resistant Staphylococcus aureus bacteria circulates both in humans and companion animals, according to a new study. Researchers also observed that samples from the ... full story

Feb. 19, 2013 — A genetically mosaic Eucalyptus tree is able to control which leaves are saved from predation because of alterations in its genes, finds a new study. Between two leaves of the same tree there can be ... full story

Sep. 22, 2011 — Maintaining fluid balance in the body is essential to survival. By researching recent genomic data, researchers have found genetic evidence that links this intricate process to a turning point in ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.